go back to your old xbox and start up the game. Recover you gamertag. Then from there it will load up and read your game history. After you get in to the main menu go and see if the medal is there. If so then all you have to do is go back to your new xbox
recover your GT and then pop the game back in and start it up and it should be there. If not call Xbox support and tell them what is going on. I had a friend who didn't have his and he called support and they were able to get it for him.

The thing is, I sold my old xbox to buy the Gears 3 one from GameStop. I actually went back twice that day to transfer data to a flash drive so I could move it to the new one, but I figured that EPIC had a better way of organizing who played in the Beta
and how much they played. But that's alright, I left a message on EPIC's voicemail. I'll never hear back :)

... So did you read this thread or not? This was established, but I explained how I bought their Gears 3 limited edition xbox yet was unable to access the features from the beta. I know I won't get the medal from the answers above, but my point is that they
needed a better way to confirm or deny who played the beta and who didn't, especially for the people interested in their new product.